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Poor Running, Worse Cold - Never 100%

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  • #31
    Check whether it really takes 90 sec. If it does then it lasts the same amount of time as the cold idle, open loop routine of a stock Motronic.
    IAT sensor inside the AFM should read ~2.5kOhms at 20C, 1.2kOhms at 40C and ~600Ohms at 60C.
    This sensor has almost no lag as opposed to the one often used for aN (PN 1718736): I did some measurements and it actually does show that it itself heats up, so I correct my statement made earlier.

    Also check the blue coolant sensor: engine cold, resistance should read something like 2kOhms and at engine operating temps something like 200 Ohms.
    A search ("blue coolant temp sensor") should yield exact numbers.

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    • #32
      Hardtailer,

      We checked the IAT awhile back and it was a bit off, as I recall. I was leaning towards doing a MAF conversion anyway as the AFM was a bit wonky as well, so that was addressed over the weekend with the Miller kit.

      Coolant sensor was replaced awhile back with minimal change. (have yet to check wiring to the DME for issues)

      So far, the cold running issue seems to have disappeared. I still have erratic light surging most noticeable under light to medium throttle/load.

      We did a Walbro fuel pump swap last summer, so I ass-u-me that fuel supply is not an issue...
      "The earth provides enough for everyone's need. Not everyone's greed." Gandhi

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      • #33
        Cold Running

        Originally posted by MauiM3Mania View Post
        Strangely, the cold running issue has gradually returned. When at operating temp, it still runs much better than before the DME swap. But for the first 90 or so seconds, it idles terribly and surges under load.

        I don't get it! And no, the rat did not return.
        Did you check the "L-shaped idle regulating valve"? Realoem.com subgroup 13, under volume air flow sensor, no. 7. I had same problem as you and consulted Mike Miller of Tech Talk on BMW Roundel magazine and he said to check this valve out and if dirty, clean it. It's a $200 part to replace, but usually just need cleaning. The other part he said to check was the coolant temp sensor which you already checked.

        Mahalo,
        Cliff49
        sigpic

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        • #34
          Cliff,

          I've not looked at the Idle Control Valve yet. So a clogged ICV can effect more than idle quality? I don't quite understand how all of this comes together.
          "The earth provides enough for everyone's need. Not everyone's greed." Gandhi

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          • #35
            Some ICVs will open when the coolant temperature is below a specific temperature. They will stay open whether the car is at idle or not, letting in additional air all the time until the car warms up. The engine control unit will also add more fuel to account for this extra air. The ICV will gradually close as the car warms up and the ECU will taper fueling to match. After the car is warmed up the ICV will only open at idle when there is extra load on the engine that would cause the RPMs to drop (like running the air conditioning).

            I don't know if the S14 ECU and ICV work like this or not. IF they do, they very well could cause the car to run overly rich until it warms up and the ECU stops injecting extra fuel. This of course assumes that the ICV failed in the closed position. (Stuck open would make you run poorly to, just in a different way.)

            The ICV can just fail on it's own and not effect anything else. Sometimes the ICV will fail and fry some components on the ECU. So if you only replace the ECU and if you have a ICV that's failed the "right" way, you could swap out ECU and fry the circuits on the new ECU too. There are several threads ECUs failing due to faulty ICVs. If you can use a soldering iron, the ECU is easy to fix. You should be able to find the threads with a little searching

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            • #36
              I pulled and cleaned, to my best ability, the ICV. The resistance is close to what is mentioned at Pelican Parts. 20 Ohms and 40 Ohms, as I recall...

              Frankly, I'm not noticing much change after the cleaning. I have yet to replace the possibly burnt chips on the DME... am I expecting too much to see some sort of improvement with just the cleaning?

              I'm unclear whether the ICV effects running of a warmed up engine at speeds other than idle. ?

              The running of the car is getting a bit better with each step, although I'm still experiencing a surge at moderate acceleration, cold or totalling warmed up. WOT, the surge is minimal.

              To recap, the following has been applied, primarily to eliminate surging, at times rough and inconsistent running.

              • New plugs, wires, cap and rotor.
              • Smoked the system, no leaks although this was done when engine was warmed up.
              • Checked compression 190 +/- 5 lbs across the board.
              • Leakdown. 95% on all four.
              • Fuel pressure was checked to be at 3 bar. Did not check pressure on the road.
              • Injectors rebuilt by RC
              • Coolant Temp Sensor
              • Fule tank cleaned, Walbro fuel pump retrofit
              • Fuel filter replaced
              • TPS replaced
              • Miller MotorSports MAF conversion


              Checking the wiring to the DME from the various sensors is on my list. I have a set of NHK plugs to replace the 3k mile old Boschs and a valve adjustment is on the list.

              Other than the wiring, I'm not expecting any great improvements from plugs or valve lash.

              Thoughts, anyone?
              "The earth provides enough for everyone's need. Not everyone's greed." Gandhi

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              • #37
                check the wiring and connectors that hook up to the fuel injector rail. i had some frayed wiring inside the plastic cover.
                Chairman of the Bored--Live Sockets Entertainment

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                • #38
                  Can you verify the CO? Don Fields used to preach this all the time.

                  Its sounds like CO and base idle adjustment is in order
                  1988 Diamantschwarz



                  "The original M3 is utterly brilliant in ways the people at M have either forgotten about or choose to ignore."

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                  • #39
                    I need to correct what I wrote in post #35 above about in the ICV affecting the way your car runs. After I don't think it will make a car run poorly the way I said it would. The ICV being stuck shouldn't really affect your AFR on a stock car. The ICV being stuck open, closed, or in-between will affect the amount of air getting into the engine. This additional air flow (or lack of it) does bypass the throttle bodies, but it does not bypass the air flow meter. The ECU should still be injecting fuel based on input from the AFM.

                    The situation I described applies to an alpha-n setup where fueling is based only on RPM and throttle position. If the stock ECU has bases some of it's warmup enrichment solely on how much the ICV is open and or closed it could affect your running condition when the ICV failed, but I doubt it works this way. Someone who knows more than me (that's a lot of people ) would have to weigh in.

                    Now a busted ICV could still affect the way your car runs but not in the way I described earlier.

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                    • #40
                      didn't want to start a new thread, but i unplugged #7 (in real oem) and nothing really changed, my idle is rough on the occasion. it runs worse when cold, but when warms up is usually steady for the most part. even weirder, my temp gauge in car is perfectly fine when cold, but as soon as gets to operating temperature, it starts bouncing around uncontrollably (as if bad ground etc, but I've checked all those already). could it be possible that the sensor is whats causing both my issues?

                      what exactly should i be seeing if i unplug the coolant sensor (#7)? (its a brown one with one plug on it.) when i unhooked the blue one, my idle shot up and was all over the place....

                      i appreciate it! - Alex

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                      • #41
                        OK, an update.

                        Since my last post in this thread, valves have been adjusted, idle control valve has been replaced and the idle did jump significantly when the temp sensor was disconnected. I think the following list is fairly complete....

                        • New plugs, wires, cap and rotor.
                        • Smoked the system, no leaks although this was done when engine was warmed up.
                        • Checked compression 190 +/- 5 lbs across the board.
                        • Leakdown. 95% on all four.
                        • Fuel pressure was checked to be at 3 bar. Did not check pressure on the road.
                        • Injectors rebuilt by RC
                        • Coolant Temp Sensor
                        • Fuel tank cleaned, etched, sealed.
                        • Walbro fuel pump retrofit
                        • Fuel filter replaced
                        • TPS replaced
                        • Miller MotorSports MAF conversion
                        • Valve clearance adjusted
                        • Idle Control Valve replaced



                        At this point, I still feel that irregular minor surge at part throttle cruise speed. And my idle is still high, sometimes as high as ~1200-1400 rpms. Other times it hovers at 1000 rpms. One thing I'm not 100% sure on is the TPS positioning, so I'll look closer at that.

                        I still am on the trail of this erratic, surging running condition.



                        Originally posted by ///CRISS View Post
                        Can you verify the CO? Don Fields used to preach this all the time.

                        Its sounds like CO and base idle adjustment is in order
                        Any further info on this would be appreciated. I assume the setting of idle and the synching of the ITBs as well are part of this operation?
                        Last edited by MauiM3Mania; 05-28-2012, 02:56 PM. Reason: clarification of idle speed
                        "The earth provides enough for everyone's need. Not everyone's greed." Gandhi

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                        • #42
                          Have you checked the intake manifold gaskets? If there original it's time for a replacement.
                          I Find your lack of faith disturbing"

                          "Objects in my rearview are losing"

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                          • #43
                            One of first things we did was smoke test the engine. No vacuum leaks were found.
                            "The earth provides enough for everyone's need. Not everyone's greed." Gandhi

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                            • #44
                              Might not be a bad idea to replace the gaskets and O-rings in the intake and throttle bodies given the fact that your idle is high. The parts are very cheap and it's not that difficult to replace them.

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                              • #45
                                With regard to the high idle, perhaps the throttle bodies could be examined for sticky/binding linkage, bent butterfly shafts plus a sticky throttle cable.

                                m

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